The present invention relates to a multilayer ceramic capacitor; and, more particularly, to a miniaturized large capacitance multilayer ceramic capacitor with an increased operating life and a method for manufacturing same, wherein the miniaturization and large capacitance are achieved by scaling down the thickness of the dielectric layers employed in the multilayer ceramic capacitor and stacking a greater number of the scaled-down dielectric layers.
In general, as shown in FIG. 1, a multilayer ceramic capacitor 10 includes a ceramic body 12 having a pair of external electrodes 14A and 14B respectively formed at two opposite end portions thereof. The ceramic body 12 is fabricated by sintering a laminated body formed of alternately stacked dielectric layers 16 and internal electrodes 18. Each pair of neighboring internal electrodes 18 faces each other with a dielectric layer 16 intervened therebetween and is electrically coupled to different external electrodes 14A and 14B, respectively.
The dielectric layers 16 are made of a reduction resistive ceramic compound including, e.g., barium titanate (BT) as a major component and an oxide of rare-earth elements. The internal electrodes 18 are formed by sintering a conductive paste whose main component is, e.g., Ni metal powder.
The ceramic body 12 is produced by forming a chip-shaped laminated body with alternately stacked ceramic green sheets and internal electrode patterns, removing a binder off the chip-shaped laminated body, sintering the binder removed laminated body in a non-oxidative atmosphere at a high temperature ranging from 1200xc2x0 C. to 1300xc2x0 C., and finally re-oxidizing the sintered laminated body in an oxidative atmosphere.
Recent trend for ever more miniaturized and dense electric circuits demands for a further scaled-down multilayer ceramic capacitor with higher capacitance. Keeping up with such demand, there has been made an effort to fabricate thinner dielectric layers and to stack a greater number of the smaller-sized dielectric layers.
However, when the dielectric layers of the multilayer ceramic capacitor are thinned out, the electric field intensity per one layer increases and, thus, the operating life of the multilayer ceramic capacitor becomes shortened.
It is, therefore, a primary object of the present invention to provide a miniaturized large capacitance multilayer ceramic capacitor with a desired operating life and a method for manufacturing same, wherein the miniaturization and large capacitance of the multilayer ceramic capacitor are achieved by scaling down the thickness of the dielectric layers in the multilayer ceramic capacitor and stacking a greater number of the scaled-down dielectric layers.
In accordance with one aspect of the present invention, there is provided a multilayer ceramic capacitor formed by alternately stacking a plurality of dielectric layers and a multiplicity of internal electrodes, which are connected to a pair of external electrodes, wherein each of the dielectric layers is obtained from a dielectric ceramic compound composed of ceramic grains and a glass component connecting the ceramic grains and the glass component contains one or more additive elements selected from the group consisting of Mn, V, Cr, Mo, Fe, Ni, Cu and Co.
In accordance with another aspect of the present invention, there is provided a method for manufacturing a multilayer ceramic capacitor, including the steps of:
forming a ceramic slurry;
forming ceramic green sheets from the ceramic slurry;
printing internal electrode patterns on the ceramic green sheets;
generating a laminated body by stacking the ceramic green sheets provided with the internal electrode patterns printed thereon;
dicing the laminated body to thereby form chip-shaped ceramic bodies; and
sintering the chip-shaped ceramic bodies, wherein the ceramic slurry includes a glass component containing one or more additive elements selected from the group consisting of Mn, V, Cr, Mo, Fe, Ni, Cu and Co.